The sense of hearing in human beings involves the use of hair cells in the cochlea that convert or transduce audio signals into auditory nerve impulses. Hearing loss, which may be due to many different causes, is generally of two types: conductive and sensorineural. Conductive hearing loss occurs when the normal mechanical pathways for sound to reach the hair cells in the cochlea are impeded. These sound pathways may be impeded, for example, by damage to the auditory ossicles. Conductive hearing loss may often be helped by the use of conventional hearing aids that amplify sound so that audio signals reach the cochlea and the hair cells. Some types of conductive hearing loss may also be treated by surgical procedures.
Sensorineural hearing loss, on the other hand, is due to the absence or the destruction of the hair cells in the cochlea which are needed to transduce audio signals into auditory nerve impulses. Thus, many people who suffer from severe to profound sensorineural hearing loss are unable to derive any benefit from conventional hearing aid systems.
To overcome sensorineural hearing loss, numerous cochlear implant systems—or cochlear prosthesis—have been developed. Cochlear implant systems bypass the hair cells in the cochlea by presenting electrical stimulation directly to the auditory nerve fibers. Direct stimulation of the auditory nerve fibers leads to the perception of sound in the brain and at least partial restoration of hearing function. To facilitate direct stimulation of the auditory nerve fibers, an array of electrodes may be implanted in the cochlea. The electrodes form a number of stimulation channels through which electrical stimulation pulses may be applied directly to auditory nerve fibers within the cochlea.
However, in some instances, the electrode array is not properly inserted within the cochlea. For example, an inserted electrode array may become folded such that one or more of the electrodes covers one or more other electrodes. An inserted electrode array may be additionally or alternatively become flipped or otherwise misaligned within the cochlea. In some instances, ossification, malformations within the cochlea, and/or other anatomical anomalies may prevent proper insertion and/or function of an electrode array that is a part of a cochlear implant system.
Once an electrode array is implanted, it may be difficult or impossible to accurately identify the cause of electrode array malfunction. Computerized Axial Tomography (“CT”) scans may be helpful in identifying such causes, but this imaging technique requires special equipment that may not be available in a clinician's office.